\r \n line insertions on Darwin to Linux in terminal

[rjkroege]

I have discovered something that seems odd. Maybe it's working as intended but it results in a lot of spurious diff mismatches for me.

When I run cpu without a Pty (i.e. by middle clicking in Acme / Edwood), command results do not contain \r characters. I.e.:

cpu -namespace $_h helios4 echo hello | od -c
0000000    h   e   l   l   o  \n                                        
0000006

But when I run cpu with a Pty (i.e. by typing in a conventional terminal, it does contain \r as part of the line endings. I.e.:

; cpu -namespace $_h helios4 echo hello | od -c
0000000    h   e   l   l   o  \r  \n
0000007

[rjkroege]

The difference would appear to be in client.go:/func.*Start

2023/08/02 05:16:48 CPU:start
2023/08/02 05:16:48 CPU:client:c.session.RequestPty("ansi", 87, 157, map[0x35:0x0 0x80:0x3840 0x81:0x3840]
2023/08/02 05:16:48 CPU:client:call session.Start(-port9p=45715 'echo' 'hello')

When executed from a terminal, the cpu client has a pty. So this block is the underlying cause of the presence of the \r.

	if c.hasTTY {
		verbose("c.session.RequestPty(\"ansi\", %v, %v, %#x", c.Row, c.Col, modes)
		if err := c.session.RequestPty("ansi", c.Row, c.Col, modes); err != nil {
			return fmt.Errorf("request for pseudo terminal failed: %v", err)
		}
	}

Hypothesis: modes needs adjustment?

[rjkroege]

Aside: why does:

func verbose(f string, a ...interface{}) {
	v("CPU:"+f+"\r\n", a...)
}

append a \r to every log message?

[rjkroege]

I hypothesize that this happens because of how gliderlabs/ssh forces the insertion of \r\n when the ssh client requested a pty. I think gliderlabs/ssh#210 (as is included in Tailscale's tailscale/tailscale#4154) would probably fix this issue.

Seems like cpu could use https://github.com/charmbracelet/ssh to fix this bug. I'll try this and update the bug.